1. Field of the Invention
The invention relates to acoustics and to sound-modifying devices or methods. More specifically, the invention relates to sound-modifying means with a sound path restriction. In another aspect, the invention relates to music and to accessories for musical instruments. More specifically, the invention relates to all types of wind instruments and especially to brasses and woodwinds having an air column contained therein that creates transverse sound waves when induced into longitudinal vibration.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a music instrument having an air column, the shape of the air column determines the resonant frequencies that will be produced by the instrument. It is known that an abrupt change in the circular cross-section of a tube introduces increased impedance and that the effect of such a discontinuity is to introduce an inductance in series with the standing waves of the air column, thereby producing a reinforced response in the instrument.
U.S. Pat. No. 3,973,464 to Donald A. Novy discloses a piston-valved brass-wind musical instrument having an exponentially offset series of reflective, elliptically constricted bore sections. The amounts of offset are based upon a percentage of the inside bore diameter taken at mid-bore length. This series of interferences, exponentially doubled at each piston's ports, creates an analogous impedance that significantly improves the response of the instrument, thereby making it easier to play and affording the player benefits of improved range, endurance, intonation and dynamic control.
U.S. Pat. No. 4,840,250 to Donald A. Novy discloses an acoustic impedance-inducing device that is axially inserted into the longitudinal air column of a wind musical instrument. This invention extended the benefits of the prior invention disclosed in the U.S. Pat. No. 3,973,464 to other types of wind instruments, including non-valved instruments.
The inserted device is structured to create a series of discontinuities in the air column. Each discontinuity is created by a ring or spiral-wound band. A series of spaced rings or bands creates two or three discontinuities. The size or radial dimension of the discontinuities should be in the ratio 1:2 or 1:2:4. Thus, if the first ring or band creates a discontinuity having an arbitrary value of one, the second discontinuity should have a radial thickness or offset of approximately twice the first; and the third discontinuity should have a thickness of four times the first. U.S. Pat. No. 4,840,250 disclosed that this structure could be achieved by a series of spiral-wound bands of appropriate lengths to form thicknesses of approximately the desired ratio when wound and inserted in the tubing or air column of a wind instrument.
Desirably, a preselected distance separates the two or more wound bands within a single inserted device. A web between each two sequential bands establishes this distance. The web is in the form of open triangles; and at each longitudinal end of the web, a normal, transverse strip connects the two bands. Further according to U.S. Pat. No. 4,840,250, each web provides a constriction between the bands, and each web blocks a portion of the neighboring bands' edges. For this reason, both the thickness of the web and the junctions with the neighboring bands have the ability to degrade the performance of the inserted coils.
It would be desirable to increase the performance of the inserted coils, or correspondingly, to reduce the degradation imposed by the web.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, the acoustic coil and method of manufacture of this invention may comprise the following.